Familial adenomatous polyposis (FAP) is an inherited susceptibility to diffuse colorectal adenomas and to colorectal carcinoma, occurring in close to 100% of unresected colons and is caused by a germline mutation in the APC gene. Most subjects who develop FAP show evidence of early adenomas between ages 10 and 15. The mutated APC gene also predisposes to duodenal polyps and to periampullary carcinoma. Although the standard of care has long been considered to be colectomy at diagnosis, practitioners and patients have been increasingly willing to undergo surveillance until there is evidence of progressive polyp burden. A recent trial demonstrated the activity of celecoxib in regressing prevalent adenomas in FAP patients with advanced adenomatous disease. This study will examine the natural history of the colorectal mucosa in young, asymptomatic carriers of APC mutations, and explore the role of celecoxib in suppressing emergence of the adenomatous phenotype. In addition, a number of ancillary evaluations will examine the relative impact of this potential preventive approach on the psychosocial status of patients.